Coffee Grinder

Coffee Grinder

Coffee grinder is the most important piece of equipment in an espresso bar. Grinders are usually overshadowed by more expensive, flashier espresso machines, but grinder quality is arguably the single most important factor in preparing a great espresso.

A quality grinder must:

• Produce the proper particle sizes to provide adequate flow resistance.

• Create a bimodal or trimodal distribution of particle sizes.

• Cause minimal heating of the grounds during grinding.

• Limit the production of fines.

Fines play many important roles in espresso percolation. For now, it is important to know that the brewing water can transport and deposit fines lower in the coffee bed during percolation, a phenomenon known as fines migration. When fines and large insoluble protein molecules are deposited at the bottom of the coffee bed, they can form a compact layer,1 or densely packed solid mass. A compact layer clogs holes at the bottom of the filter basket and can result in obstruction of flow paths, uneven resistance to flow, and channelling. It is desirable to have some fines, but too many fines or too much fines migration can damage espresso quality.

Source: The Professional Barista’s Handbook by Scott Rao